Reticle design for alternating phase shift mask

Abstract

The present invention provides a method and apparatus for producing 0 degree light and 180 degree phase shifted light having substantially equal intensities as both lights exit an alternating phase shift reticle. A material is inserted within the etched portion of the 180 degree phase shift channel of a reticle, wherein the material contains an index of refraction such that the first order light (+1, −1) is propagated through the 180 degree channel. The end result is a 180 degree phase shifted light having an intensity substantially equal to that of the 0 degree light.

What is claimed as new and desired to be protected by Letters Patent of the United States is:  
     
       1. An alternating phase shift reticle, comprising: 
       a substrate having a 0 degree light path and an etched 180 degree phase shifted light path therein; and  
       a material provided in at least one of said 0 degree and said etched 180 degree paths which causes an intensity of light exiting said etched 180 degree light path to be approximately equal to an intensity of light exiting said 0 degree light path, said material being separate from either of said 0 degree and said etched 180 degree light paths.  
     
     
       2. The reticle of  claim 1 , wherein said substrate is quartz. 
     
     
       3. The reticle of  claim 1 , wherein said material is provided in said 180 degree light path. 
     
     
       4. The reticle of  claim 1 , wherein said material is provided in both said 0 degree and said 180 degree light paths. 
     
     
       5. The reticle of  claim 1 , wherein said material contains a predetermined index of refraction and a predetermined depth. 
     
     
       6. The reticle of  claim 5 , wherein said material is adapted to transmit light rays from said etched portion of said 180 degree light path to a light exiting portion of said 180 degree light path. 
     
     
       7. The reticle of  claim 6 , wherein said material is adapted to direct light rays entering said etched portion at a predetermined angle such that said light rays exit said 180 degree light path. 
     
     
       8. The reticle of  claim 7 , wherein said material is configured to direct said light rays toward a sidewall of said etched portion such that a critical angle is formed, thereby redirecting said light rays in a direction parallel with said sidewall. 
     
     
       9. An alternating phase shift reticle, comprising: 
       at least one 0 degree optical channel adapted to transmit a first set of light rays of a first intensity; and  
       at least one etched 180 degree optical channel adapted to transmit a second set of light rays, said second set of light rays having a second intensity, wherein  
       said at least one etched 180 degree channel is at least partially filled with a material having a depth and an index of refraction such that said first and second intensities are approximately equal, said material being separate from either of said 0 degree and etched 180 degree channels.  
     
     
       10. The alternating phase shift reticle of  claim 9 , wherein said at least one 0 degree optical channel is at least partially filled with said material. 
     
     
       11. A method of forming an alternating phase shift reticle, the method comprising: 
       providing a substrate having a 0 degree and an etched 180 degree phase shifted light path; and  
       providing a material in at least one of said 0 degree and said etched 180 degree paths which causes an intensity of light exiting said etched 180 degree light path to be approximately equal to an intensity of light exiting said 0 degree light path, said material being separate from either of said 0 degree and said etched 180 degree light paths.  
     
     
       12. The method as in  claim 11 , wherein said act of providing a substrate comprises providing a quartz substrate. 
     
     
       13. The method as in  claim 11 , wherein said act of providing a material comprises providing a filling material having a predetermined index of refraction and a predetermined depth within an etched portion of said 180 degree phase shifted light path. 
     
     
       14. An alternating phase shift reticle, comprising: 
       a substrate having a 0 degree light path with a first length;  
       a 180 degree phase shifted light path etched in said substrate with a second length shorter than said first length;  
       a material provided in an etched portion of said 180 degree phase shifted light path that extends said second length to be approximately equal to said first length; and wherein  
       said material causes an intensity of light exiting said 0 degree and 180 degree light paths to be substantially equal.  
     
     
       15. The reticle of  claim 14  further comprising: 
       a light non-transmissive region of said substrate adjacent to both said 0 degree and said 180 degree light paths, said light non-transmissive region extending to a third length beyond said first length, wherein  
       said material provided in said etched portion of said 180 degree phase shifted light path extends approximately to said third length; and wherein  
       said material is provided at an end of said 0 degree light path and extending approximately to said third length.